During the manufacture of a liquid crystal panel, after the alignment of the colored film (CF) substrate and the array substrate, liquid crystal is filled between the colored film substrate and the array substrate, and the peripheries are sealed with glue, namely the sealant. Commonly used sealants primarily comprise an ultraviolet polymerizable double bond monomer, a thermal polymerization monomer, a photoinitiator, a heat curing agent, and a particulate additive, etc.
Commonly used sealants are cross-linked by stepwise polymerization. First, ultraviolet polymerization is conducted, which generates free radicals from the photoinitiator by ultraviolet irradiation. The free radicals initiate the chain polymerization of the ultraviolet polymerizable double bond monomer to generate a high molecular polymer. During this process, since the rate of the polymerization of the heat polymerization monomer is slow, and the rate of the polymerization of the ultraviolet polymerizable double bond monomer is fast, the high molecular polymer generated by the polymerization of the ultraviolet polymerizable double bond monomer can thus anchor the heat polymerization monomer in the sealant, blocking the diffusion of the heat polymerization monomer into the liquid crystal, preventing the contamination of the liquid crystal by the sealant, thereby avoiding the appearance such as yellowing and unevenness in the peripheries of the liquid crystal panel. After the completion of the ultraviolet polymerization, the heat polymerization is conducted, during which the heat polymerization monomers are polymerized to generate a high molecular polymer with good mechanical performance, thereby effectively binding the colored film substrate and the array substrate.
Studies on anchoring surrounding small molecular by polymer network are introduced in the following publications:
[1] Guo J B, Sun J, Zhang L P, Li K X, Cao H, Yang H, Zhu S Q, Polym Advan Technol, 2008: 19: 1504-1512.
[2] Guo J B, Sun J, Li K X, Cao H, Yang H. Liq Cryst, 2008: 35: 87-97.
[3] Guo R W, Cao H, Yang C Y, Wu X J, Meng Q Y, Liu T, He W L, Cheng Z H, Yang H. Liq Cryst, 2010: 37: 311-316.
Currently, the high molecular polymers generated by photoinitiators from ultraviolet polymerizable double bond monomers during the ultraviolet polymerization of the existing sealant are mostly linear, which cannot effectively anchor heat polymerization monomers, so that there are still a portion of heat polymerization monomers diffusing into and thus contaminating the liquid crystal.